Mode Conversion Processes from Electrostatic Plasma Waves into Electromagnetiic Waves in the Space Plasma

静电等离子体波向电磁波的模式转换过程是空间等离子体产生电磁辐射的主要过程之一。本文利用Akebono卫星等离子体波探测器（PWS）的观测数据和地面观测数据，研究了地球射电辐射（THR）、极光千米辐射（AKR）和木星十米波辐射（DAMs）的模转换过程。对于THR，我们发现在1.7MHz和3.4MHz这两个固定频率处产生了THR的强波，这些波是在源的UHR频率为本振电子回旋频率的两倍的条件下产生的。对于强R-X模AKR，人们发现多普勒转换过程是重要过程之一，回旋脉泽过程并不是AKR唯一的产生机制。对于木星S-暴的产生机制，阐明了S-暴的产生不能用源区与观测者之间的几何效应来解释，而是表明了电子束在沿着与卫星Io相连的磁力线瞬间形成了加速区。

The mode conversion process from electrostatic plasma waves into electromagnetic waves is one of the main processes to produce electromagnetic radiations in the space plasma. In the present study, we have investugated the mode conversion proceses taking place in the terrestrial hectomrtric radiations (THRs), auroral kilometric radiations (AKRs)and Jovian decametric radiations (DAMs) by using the data of plasma wave detector (PWS) onboard the Akebono satellite as well as the data obtained by the ground based observations. As for the THRs, we have found that strong componets of THRs are generated at the fixed frequencies of 1.7MHz and 3.4MHz ; these waves are generated by the condition that the UHR frequency of the source becomes the twice of the local electron cyclotron frequency. For the intense R-X mode AKRs, it has been found that the Doppler conversion process is one of the important processes, and the cyclotron maser process is not the unique generation mechanism of AKRs. Further for the generation mechanism of the Jovian S-bursts, it has been clarified that the occurrence of S-bursts can not be explained by the gometrical effect between the source region and the observer, but it rather indicates the formation of the acceleration region of electron beam at the moment along the magnetic field line which is connected to the satellite Io.